Icerya purchasi

Image:Icerya purchasi 1435060.jpg

This scale infests twigs and branches. The mature hermaphrodite is oval in shape, reddish-brown with black hairs, 5 mm long. When mature, the insect remains stationary, attaches itself to the plant by waxy secretions, and produces a white egg sac in grooves, by extrusion, in the body which encases hundreds of red eggs. The egg sac will grow to be two to three times as long as the body. Newly hatched nymphs are the primary dispersal stage, with dispersion known to occur by wind and by crawling. Early stage nymphs feed from the midrib veins of leaves and small twigs, and do the bulk of the damage. At each molt, they leave at the old feeding point the former skin and the waxy secretions in which they had covered themselves and from which their common name is derived. Unlike many other scale insects, they retain legs and a limited mobility in all life stages. Older nymphs migrate to larger twigs and eventually as adults to branches and the trunk. Their life cycle is highly temperature-dependent, as the length of time in each stage of life is longer in cold temperatures than high temperatures.

In addition to the direct damage from sap sucking, the insects also secrete honeydew, on which sooty mold often grows and causes further damage to the host plant. Some ants will also consume this honeydew.

File:Icerya_purchasi_male.jpg

Males are rare in hermaphroditic species of Icerya. Males are haploid while females are diploid. Females have an ovitestis that is capable of producing both sperm and oocytes which fertilize internally to produce diploid offspring (females) through a form of hermaphroditism. The cells of the ovitestis are haploid and are derived from excess sperm during matings with males. This has been termed as 'parasitic tissue' and theoretical studies have examined this as a form of sexual conflict and have examined the possible fates and fitness consequences since females can produce daughters by mating with males or using their parasitic male cell lines. Females that lack ovitestes may preferentially invest in producing sons while females with parasitic tissue should prefer to pass on the genetic material through daughters.{{cite journal| title=The Evolution of Hermaphroditism by an Infectious Male-Derived Cell Lineage: An Inclusive-Fitness Analysis|first1= Andy |first2=Gardner |last1= Laura|last2= Ross| journal= The American Naturalist|volume=178| issue= 2 |year=2011| pages= 191–201|doi=10.1086/660823 |pmid= 21750383 |s2cid= 15361433 |url= https://pure.rug.nl/ws/files/67294482/660823.pdf |hdl= 11370/c2d17516-c096-4e53-80a1-d79b3aab10b3|hdl-access= free}}

True males are uncommon to rare overall, and in many infestations are not present. Pure females are unknown. Self-fertilization by a hermaphrodite will produce only hermaphrodites. Matings of a male and hermaphrodite will produce both males and hermaphrodites.{{cite journal |first1=Andy |last1=Gardner |first2=Laura |last2=Ross |year=2011 |title=The Evolution of Hermaphroditism by an Infectious Male-Derived Cell Lineage: An Inclusive-Fitness Analysis |journal=The American Naturalist |volume=178 |issue=2 |pages=191–201 |doi=10.1086/660823 |pmid=21750383|s2cid=15361433 |url=http://www.press.uchicago.edu/ucp/journals/journal/an.html |hdl=11370/c2d17516-c096-4e53-80a1-d79b3aab10b3 |hdl-access=free}}

• {{cite magazine |author=Christine Dell'Amore |date=August 17, 2011 |title=Cloned Fathers Mate With Insect Daughters—From Inside |magazine=National Geographic |url=http://news.nationalgeographic.com/news/2011/08/110817-insects-sex-hermaphrodites-science-evolution-clones-mate-fathers/ |archive-url=https://web.archive.org/web/20111015122708/http://news.nationalgeographic.com/news/2011/08/110817-insects-sex-hermaphrodites-science-evolution-clones-mate-fathers/ |archive-date=2011-10-15}}

File:Rodolia cardinalis USDA.jpg, known as the Vedalia beetle, feeding on cottony cushion scale]]

Icerya purchasi is important as one of the first major successes of biological control. Importations of the vedalia ladybird (Novius cardinalis) in 1888–1889 by C. V. Riley, later head of the USDA's Division of Entomology, resulted in swift reductions of I. purchasi populations, saving the burgeoning Californian citrus industry from this destructive pest.{{cite journal |last1=Quezada |first1=José R. |last2=DeBach |first2=Paul |title=Bioecological and population studies of the cottony-cushion scale, Icerya purchasi Mask., and its natural enemies, Rodolia cardinalis Mul. and Cryptochaetum iceryae Will., in southern California |journal=Hilgardia |date=April 1973 |volume=41 |issue=20 |pages=631–688 |doi=10.3733/hilg.v41n20p631|doi-access=free }} However, following the introduction of insecticides such as DDT and malathion in the 1950s further outbreaks occurred due to resurgence: thought to be caused by drift from airplane spraying during the early spring months.Bartlett BR, Lagace CF (1960) Interference with the biological control of cottony-cushion scale by insecticides and attempts to re-establish a favorable natural balance. Journal of Economic Entomology, 53 [6] 1055–1058.

A second biological control, the parasitic fly Cryptochetum iceryae, has also been introduced to California as an additional control vector at around the same time.

While there is an apparent rivalry between the two natural enemies of Icerya purchasi, the competition does not affect the efficacy of the control measures when both the beetle and the fly are introduced. Biological control remains the most effective measure to manage Icerya purchasi infestations.{{cite web |title=Cottony Cushion Scale Management Guidelines--UC IPM |url=http://ipm.ucanr.edu/PMG/PESTNOTES/pn7410.html |website=ipm.ucanr.edu}} Use of insecticides as control is recommended only if no biological control species is present. Imidacloprid is especially contraindicated, since it has no effect on this species, but is very toxic to Novius cardinalis.

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• {{cite web |url=http://entomology.ifas.ufl.edu/creatures/fruit/cottony_cushion_scale.htm |title=Cottony cushion scale, Icerya purchasi Maskell |access-date=2008-07-16 |author1=Hamon, A. B. |author2=Fasulo, T. R. |year=2005 |publisher=University of Florida}}
• {{cite web |url=http://www.ars.usda.gov/is/timeline/insect.htm |title=ARS Timeline: History of Research at the U.S. Department of Agriculture and Agricultural Research Service |access-date=2008-07-16 |date=2008-07-07 |publisher=USDA Agricultural Research Service |archive-url=https://web.archive.org/web/20070714102936/http://www.ars.usda.gov/is/timeline/insect.htm |archive-date=2007-07-14 |url-status=dead }} (originally published as 20th Century Insect Control in the July 1992 issue of Agricultural Research magazine)
• {{cite web |url=http://www.ces.ncsu.edu/depts/ent/notes/O&T/shrubs/note51/note51.html |title=Cottony Cushion Scale |access-date=2008-07-16 |last=Baker |first=James R. |date=July 1994 |work=Ornamentals and Turf: Department of Entomology Insect Note |publisher=North Carolina State University |archive-url=https://web.archive.org/web/20080515113222/http://www.ces.ncsu.edu/depts/ent/notes/O%26T/shrubs/note51/note51.html |archive-date=2008-05-15 |url-status=dead }}
• {{cite web |url=http://edis.ifas.ufl.edu/CH059 |title=Scale Pests of Florida Citrus |access-date=2008-07-16 |author1=Fasulo, T. R. |author2=Brooks, R. F. |orig-date=October 1993 |date=June 2004 |publisher=Entomology and Nematology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida |archive-url=https://web.archive.org/web/20000512020944/http://edis.ifas.ufl.edu/CH059 |archive-date=2000-05-12 |url-status=dead}}
• {{cite web |url=http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7410.html |title=Cottony Cushion Scale |access-date=2008-07-16 |last=Grafton-Cardwell |first=E. E. |date=December 2003 |work=How to Manage Pests: Pests in Gardens and Landscapes |publisher=University of California Statewide Integrated Pest Management Program}}

• {{cite web |url= http://anrcatalog.ucdavis.edu/pdf/8051.pdf |title= Life cycle stages of the Cottony Cushion Scale and Vedalia Beetle in high quality pictures |access-date= 2008-07-16 |archive-url= https://web.archive.org/web/20090509051453/http://anrcatalog.ucdavis.edu/pdf/8051.pdf |archive-date= 2009-05-09 |url-status= dead }}

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Category:Monophlebidae

Category:Citrus pests

Category:Agricultural pest insects

Category:Insects described in 1878

Category:Hemiptera of Australia

Category:Incestuous animals